In the diagram you showed the diffrence between a wye and delta configuration is wye is 208v and delta is 240v. In the wye setup each on of the legs reads 120 to ground or neutral and in delta you have a stinger leg of about 205v to ground or neutral. Your grinder looks to be only 240v rated. If it had more wires it possibly could be set up to run at 480v also, depending on how you tap it at the peckerhead.